Sacramento River

Gage Gap

Nature Conservancy | October 31st, 2018

Following a difficult five-year drought, California just had one of the wettest winters on record. The state is famous for its highly engineered water system, whi

Following a difficult five-year drought, California just had one of the wettest winters on record. The state is famous for its highly engineered water system, which moves millions of gallons of water from north to south and east to west. Thirty-nine million people and our $47 billion agricultural industry rely on that water, not to mention wildlife from the Sierra to the sea. And yet we have surprisingly little data about how much water is moving through our streams at any given time. There are over 3,600 locations in California where stream gages have been active at some point, but only 54% have been active recently. And even fewer of those provide the kind of rich, real-time reporting needed to manage what is arguably our state’s most precious and contentious resource.

Geochemistry of Ground Water in the Sacramento Valley, California

U.S. Geological Survey (USGS) | July 13th, 1984

A geochemical investigation was done to evaluate temporal changes in water quality and to determine the processes that control water chemistry in shallow ground water of

A geochemical investigation was done to evaluate temporal changes in water quality and to determine the processes that control water chemistry in shallow ground water of the Sacramento Valley, California. A total of 671 chemical analyses from 651 wells were used to study the processes controlling water chemistry. Temporal variations in dissolved-solids and nitrate concentrations were studied in 140 and 62 wells, respectively, having multiple observations with time.

Geohydrology and Numerical Model Analysis of Ground-Water Flow in the Goose Lake Basin, Oregon and California

U.S. Geological Survey (USGS) | December 15th, 1988

From the early 1970s until 1981, ground-water development in the Goose Lake basin underwent rapid growth. The number of new wells constructed and total State-perm

From the early 1970s until 1981, ground-water development in the Goose Lake basin underwent rapid growth. The number of new wells constructed and total State-permitted ground-water withdrawals for irrigation reflect the increase in ground-water development that occurred during this period. A strong agricultural economy spurred much of the development by providing incentives to expand irrigated acreage and modernize irrigation methods (from gravity to sprinkler systems). The drought of 1976-77 also encouraged farmers to develop ground water as a supplemental source to less reliable surface-water supplies used in the past. A preliminary assessment of the basin by OWRD staff (R. B. Almy, Oregon Department of Water Resources, written commun., 1981) concluded that, based on rates of water-level decline and increases in withdrawals, further and more detailed study of the basin was warranted. Between 1975 and 1982, water-level declines in some OWRD observation wells ranged from 0.5 to 3 feet per year, while permitted ground- water withdrawals increased at an average rate of 4,000acre-feetperyear(acre-ft/yr). Similarwater-level declines and increases in withdrawals occurred near Davis Creek on the California side of the basin during this period. This prompted a 1982 assessment of ground-water conditions by the California Department of Water Resources (California Department of Water Resources, 1982). At the time of OWRD's assessment it was felt that too little information on the actual rates of ground-water use, recharge, and the geohydrology of the aquifer system was available to allow proper management of the resource. If the rates of water-level decline and ground-water withdrawal that existed prior to 1981 had continued, issuance of new permits for ground-water use potentially could have been halted in order to determine if the Goose Lake basin should be designated as a "criticalground-water area." Sucha designation would allow the State of Oregon to limit the use of ground-water resources in the area. However, overdraft of the ground-water resource became a less urgent issue after 1982, when a downturn in the agricultural economy, combined with rising costs of electrical power (and thus pumping), resulted in a widespread reversion to dryland farming and low-water-use crops. Adverse agricultural market conditions halted the growth of ground-water development in the basin; these trends could conceivably reverse in the future to spur growth again. In recognition of this potential and the need to build an understanding of the basin in order to properly manage future ground-water development, OWRD entered into a joint program of study with the U.S.Geological Survey. The first of a proposed series of ground-water basin assessments, this 1-year study was started in 1986 with the goals of characterizing the nature, extent, and properties of water-bearing rocks within the basin and describing and quantifying the components of recharge to, and discharge from, the basin. Additionally, this study was designed toe valuate the adequacy of available and readily collectable information to quantitatively describe the geohydrology of the basin. If this information was found to be inadequate, the study would also identify the data needed to better describe, understand, and manage the ground-water resource.

Geologic Influences on the Quality of Groundwater Used for Domestic Supply in the Northern Sierra Nevada Foothills

U.S. Geological Survey (USGS) | May 25th, 2021

Approximately 2 million California residents depend on groundwater from domestic wells for their drinking-water supply. The State of California, in collaboration with the

Approximately 2 million California residents depend on groundwater from domestic wells for their drinking-water supply. The State of California, in collaboration with the U.S. Geological Survey, created the Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) to assess the quality of groundwater used for domestic supply throughout the state and determine regional vulnerabilities to drinking-water resources. Many rural households in the northern Sierra Nevada foothills (hereafter referred to as “the foothills”) use domestic wells that pump water from fractured-bedrock aquifers. In the foothills, complicated and varied regional bedrock geology can cause substantial variation in groundwater chemistry and quality over relatively short distances. This factsheet presents findings from the GAMA-PBP assessment that highlight influences of geologic factors on groundwater quality in the foothills.

Geology of Northern California Bulletin 190

California Division of Mines and Geology | December 1st, 1966

Geology of the Fresh Ground‐water Basin of the Central Valley, California, with Texture Maps and Sections

U.S. Geological Survey (USGS) | December 1st, 1986

The Central Valley of California, which is about 400 miles long and averages about 50 miles wide, comprises about 20,000 square miles. Geologically, the valley is

The Central Valley of California, which is about 400 miles long and averages about 50 miles wide, comprises about 20,000 square miles. Geologically, the valley is a large asymmetric trough that is bounded by granitic, metamorphic, and marine sedimentary rocks of pre-Tertiary age. The trough has been filled with as much as 6 vertical miles of sediment in the San Joaquin Valley and as much as 10 vertical miles of sediment in the Sacramento Valley; these sedi- ments range in age from Jurassic to Holocene. Some volcanic rocks and deposits crop out in the valley, but of those only the Tuscan Formation in the northeastern part of the Sacramento Valley is of major importance to the fresh ground-water basin. Post-Eocene continental rocks and deposits contain most of the fresh water in the Central Valley; they crop out virtually over the whole valley and in most places overlie or contain saline water at depth. Continental rocks and deposits of Tertiary age include the Mehrten Formation. The Mehrten is of great importance to the fresh ground-water basin of the Central Valley and yields large quantities of water to wells.

Geology of the fresh ground‐water basin, Central Valley, California, with texture maps and sections

U.S. Geological Survey (USGS) | July 17th, 1986

The Central Valley of California, which is about 400 miles long and averages about 50 miles wide, comprises about 20,000 square miles. Geologically, the valley is

The Central Valley of California, which is about 400 miles long and averages about 50 miles wide, comprises about 20,000 square miles. Geologically, the valley is a large asymmetric trough that is bounded by granitic, metamorphic, and marine sedimentary rocks of pre-Tertiary age. The trough has been filled with as much as 6 vertical miles of sediment in the San Joaquin Valley and as much as 10 vertical miles of sediment in the Sacramento Valley; these sedi- ments range in age from Jurassic to Holocene. Some volcanic rocks and deposits crop out in the valley, but of those only the Tuscan Formation in the northeastern part of the Sacramento Valley is of major importance to the fresh ground-water basin. Post-Eocene continental rocks and deposits contain most of the fresh water in the Central Valley; they crop out virtually over the whole valley and in most places overlie or contain saline water at depth. Continental rocks and deposits of Tertiary age include the Mehrten Formation. The Mehrten is of great importance to the fresh ground-water basin of the Central Valley and yields large quantities of water to wells. Although continental rocks and deposits of Tertiary and Quaternary age compose a number of formations and informal deposits, in total they constitute the major aquifer of the Central Valley. In most places, similarity in sediment type between the continental deposits and some underlying rocks and deposits and even between separate units of continental rocks and deposits makes mapping of subsurface geologic contacts difficult if not practically im- possible. In this respect, a unit that can be mapped on the surface is difficult to delineate in the subsurface, and, although such a unit can be called an aquifer, it merges with similar units in the subsurface to form a major, widespread aquifer. Continental rocks and deposits of Tertiary and Quaternary age include (1) the Kern River Formation; (2) the Laguna Formation; (3) the Tulare Formation; (4) the Tehama Formation; and (5) a number of younger formations, as well as some informally named deposits. These deposits and formations also include lacustrine and marsh deposits, which are much thicker and more extensive in the San Joaquin Valley than in the Sacramento Valley. These continental rocks and deposits generally crop out as wide belts along the flanks of the Central Valley and range in thickness from 0 foot along the flanks to about 15,000 feet in the extreme southern part. In general, the rocks and deposits consist of a heterogeneous mixture of generally poorly sorted clay, silt, sand, and gravel; in some places they consist of more consolidated sediments, such as mudstone and sandstone. Yields to wells from these rocks and deposits, except the lacustrine and marsh deposits, range from about 20 gallons per minute to 4,500 gallons per minute. Lacustrine and marsh deposits crop out in the San Joaquin Valley but not in the Sacramento Valley. Beneath Tulare Lake bed in the San Joaquin Valley, the lacustrine and marsh deposits, which constitute a thick plug of clay and silt from which lenses of clay and silt emanate at irregular intervals, are in places more than 3,600 feet thick. The lens mapped as the E Clay in the San Joaquin Valley is the most extensive lacustrine clay in the entire Central Valley and includes the Corcoran Clay Member of the Tulare Formation. More recent mapping has shown that the E Clay in the extreme southern part of the valley is shallower than previous reports had indicated; therefore, in this report the clay is referred to as the modified E Clay. Perhaps the expansion of lakes and the resulting deposition of extensive clays in the San Joaquin Valley occurred principally because of a large downwarping basin beneath an area known as Tulare Lake bed, and perhaps a similar expansion and deposition did not occur in the Sacramento Valley because a similar downwarping basin probably had not developed there. Continental deposits of Quaternary age crop out chiefly along the major rivers and streams of the valley as well as other low-lying areas; the deposits include river deposits, flood-basin deposits, and sand dunes. River deposits, including channel and flood-plain depos- its, are considered to be the most permeable deposits in the valley; in general, they are not tapped by wells. Flood-basin deposits consist largely of fine-grained beds that restrict the vertical movement of water. Sand dunes are not considered important aquifers because they generally lie above the water table. The large, asymmetrical, northwestward-trending structural trough of the Central Valley is the principal structure controlling the occurrence and movement of ground water in the area. Because the flanks of the valley are higher than its axis, recharge from tributary rivers and streams has caused heads in the ground water along the flanks to be higher than those along the axis. Therefore, the overall ground-water movement in the Central Valley is from the flanks toward the axis and from there toward the delta area. Secondary structures in the valley, such as arches and faults, also influence the occurrence and movement of ground water. As it is used in this report, "texture" means the proportion of coarse-grained to fine-grained sediment in sedimentary rocks and deposits. In the Central Valley, most of the deposits for which data are available generally contain no more than 40 to 60 percent of coarse-grained sediment, where coarse-grained sediment includes clayey and silty sand and gravel. Texture columns, maps, and sections, in depth intervals of 300 feet, show that the alluvial deposits of the Central Valley are a heterogeneous mixture whose character ranges over short distances and depths from chiefly fine-grained to chiefly coarse-grained and vice versa. Nevertheless, some areas are underlain chiefly by fine-grained sediment and others by coarse-grained sediment; sediments of like size in an area indicate that sources and depositional environment probably were similar for long periods of time.

Geology of the Northern Sacramento Valley, California

California Department of Water Resources (DWR) | September 22nd, 2014

This study describes the complex geology of the northern Sacramento Valley, focusing on the Late Cenozoic geologic formations and structures that compose or influence the

This study describes the complex geology of the northern Sacramento Valley, focusing on the Late Cenozoic geologic formations and structures that compose or influence the valley’s fresh groundwater aquifer formations. The California Department of Water Resources (DWR) acquired geologic data from groundwater observation well drilling operations that were conducted in the valley over the last 15 years. Using the observation well drilling data, DWR evaluated and classified the lithology of the subsurface sediments, implemented petrographic sand provenance analyses on lithologic sediment samples, and reviewed associated geophysical logs from each bore hole. In addition, DWR conducted an extensive literature review of published and unpublished data and then integrated the data to produce this geologic report, map, and cross sections that describe the geology of the northern Sacramento Valley. Results from the lithologic logging, petrographic analyses, and data review show that the heterogeneous sediments of the northern Sacramento Valley’s most productive groundwater-bearing geologic formations, the Tehama Formation and the Tuscan Formation, intermix in the subsurface in various areas near the center of the valley. The results also show that toward the westward and eastward extents of the valley, the sediments of the formations become more unified in composition due to the proximity of their respective sediment source areas. However, because of the depositional environment of the geologic formations, sediment sizes within the formations can be discontinuous and intermittent in places, resulting in variable groundwater aquifer zones within the geologic formations. Additional data are needed to further define the northern Sacramento Valley aquifer system. Drilling and installing groundwater observation wells in areas of little or no data can provide the information needed to determine the extent and variability of the valley’s groundwater aquifers. Groundwater level data supplied by the observation wells can provide valuable information for monitoring aquifer conditions, for determining the change in groundwater levels over time, and for assessing the ability of groundwater to move through the geologic aquifer sediments. In addition, a textural analysis of formational sediments using lithologic cuttings and/or driller’s well logs could be performed to better identify aquifer production zones. In summary, the geology of the northern Sacramento Valley is diverse and has a widely varied historical sequence of earth-shaping events. It includes periods of time when much of the area was below sea level, multiple and distinct periods of volcanic activity, several periods of mountain building, and intermingled periods of massive erosion and deposition. Analyses of the data illustrate the heterogeneity of the groundwater-bearing geologic formations in the subsurface, and the intermixing of formational sediments toward the center of the northern Sacramento Valley, resulting in a region with great geologic and hydrogeologic complexity.

Geology, water resources and usable ground-water storage capacity of part of Solano County, California

U.S. Geological Survey (USGS) | July 1st, 1960

The area described is confined largely to the valley-floor and foothill lands of Solano County, which lies directly between Sacramento, the State capital, and San Franc

The area described is confined largely to the valley-floor and foothill lands of Solano County, which lies directly between Sacramento, the State capital, and San Francisco. The area is considered in two subareas: The Putah area, which extends from Putah Creek southward to the Montezuma Hills and from the foothills of the Coast Ranges eastward to the west edge of the Yolo Bypass; and the Suisun-Fairfield area, which is to the southwest in the notch in the Coast Ranges through which the waters of the Great Central Valley of California reach San Francisco Bay. There are no known hydrologic interconnections between the two subareas, through either surface streams or underground aquifers. The climate of the area is characterized by warm, rainless summers and by cool winters in which temperatures seldom drop much below freezing. The rainfall ranges from about 17 inches per year along the east side to perhaps 24 inches in the foothills to the west, and irrigation is necessary for all crops except dry-farmed grains, pastures, and some orchards.

Gill Net Selectivity for Fifteen Fish Species of the Upper San Francisco Estuary

University of California, Davis (UC Davis) | July 14th, 2022

Gill-net size selectivity for fifteen fish species occurring in the upper San Francisco Estuary was estimated from a data set compiled from multiple studies which togethe

Gill-net size selectivity for fifteen fish species occurring in the upper San Francisco Estuary was estimated from a data set compiled from multiple studies which together contained 7,096 individual fish observations from 882 gill net sets. The gill nets considered in this study closely resembled the American Fisheries Society’s recommended standardized experimental gill nets for sampling inland waters. Relationships between gill-net mesh sizes and the sizes for each fish species retained in them were estimated indirectly using generalized linear modeling and maximum likelihood. Selectivity curves are provided for each species to inform researchers about population characteristics of fishes sampled with similar gill nets.